I will always encourage people to use an appropriately sufficient cable to get the job done without issues, but that is a very small step compared to upgrading to a $500 10 foot HDMI cable from Monster Cables (which is what the advertisement was pushing).
With 4K being new, I am certain there are plenty of cables out there in the world which will struggle to get the job done sufficiently. And surely many of us may need to upgrade our trusty HDMI cables when we finally move to a 4K UHD TV over the next few years. But I would argue that it would likely never occur that a costly cable sold at a massive premium from Best Buy would make a huge difference (or any difference) in the picture quality over a well designed and built cable from a trustworthy source, like Blue Jeans Cables.
With 4K being new, I am certain there are plenty of cables out there in the world which will struggle to get the job done sufficiently. And surely many of us may need to upgrade our trusty HDMI cables when we finally move to a 4K UHD TV over the next few years. But I would argue that it would likely never occur that a costly cable sold at a massive premium from Best Buy would make a huge difference (or any difference) in the picture quality over a well designed and built cable from a trustworthy source, like Blue Jeans Cables.